This is the setup I have:

355 10:1 vortec heads, edelbrock perf rpm intake, LT4 hot cam hyd roller (.525"), should be making about 400hp.

So in the 1/8th mile with a holley 3310 780 vacuum secondary the best I ran was 8.10. I went to a 650 street hp double pumper and the fastest I could go was 8.13. I tuned both carbs the best I could. I thought a 650 would be perfect for a 355 but does this mean I need to go bigger? This car is a street car also.

 

A "well tuned" 650 double pumper should be plenty for a mild 355...look into timing and/or fuel delivery for more gains provided everything else is up to spec. What trans, rear gearing, converter etc. do you have? 8.10-8.13 in the 1/8th mile is not too shabby for a mild 355 on motor either.

 

trans is 700r4 w/ shift kit and edge 3000 stall and 3.27 9bolt gears

 

What did the time slip look like, MPH, 60 foot ect?

 

I'm not even sure why you'd suggest that you'd think it was too small a carb, you dropped from 780 to 650cfm and only lost .03seconds...

 

this is proof that sometimes a vac secondary carb can be better in some cases. we all know the guy who swears by a DP.

 

I figured a double pumper would be at least a tenth faster.

 

basically no change means that either one is sufficient...Stick with double pumper...Also check to be sure that you getting enough fuel volume to the carb... Is your pump sufficient enough to supply the carb..?? you need another 1000 rpm worth of stall and a 4.10 in that thing..

 

I know I need some gears.. I got 4.10s in my '87 I could swap rears would the 4.10s be too much with the 700r4s low first gear? Everyone keeps telling me the 700r4 is junk for racing because of the gear spread

 

its not the greatest but its not that bad...you should definitely try the 4.10's if you have em.._as long as the car hooks well...

 

The gear drop isnt jack if you are making power or have a decent stall, the first gear in the 700R is awesome though, gets some great 60 foot times over the standard TH350 first gear.

 

a carb is to small only if you have vaccum in the intake manifold @ WOT. - Unless you're way over-reving it for the cam spec, a 650 is none-to small. Until I went north of 6800rpm with a well built 355(with considerably more cam) I had next-to-no peak hp difference when switching between a 650 and 750, and a definite loss in driveability and low-mid range with the 750.

Likely gearing is a big factor in your combo not performing as you feel it should.

 

Consider tuning for MPH instead of ET. A small slip of the tire can throw ET off, IMHO tuning for MPH is the better way.

 

I personally love the 3310 which is typically rated at 750cfm. I had one on a 353 with ported l98 heads and a mid sized hyd roller in a swb truck and got 17mpg with a 700r4 and 308 gears and the truck ran 14.50's 1/4 mile. You can tune that 3310 to respond like a double pumper by changing the springs in the secondary's. Holley even makes a quick change kit.

also make sure your vac advance is working most people over look that.

 

I just tuned it on a dyno last night, gained about 12hp, ended up with 67/75 jets and 33* total timing.

 

What kind of power did you make?

 

was that jetting with the 650 carb or 750 3310 carb ?

There are a few (more advanced tuning) tricks you can do to the 3310 vac sec system beyond just springs to get it "just right".

Just like dialing in a double pumper for max performance the vs carbs need a good bit of patient trial and error tweeking at the track to get them right. Then they fly.

 

Now I remember why I like my Edelbrock so much. So much less working and tuning on one.